Questions about upgrading

I have a Powerbook G4 PPC laptop and realize it's just too old to be fully useful. If I get a used Intel based laptop, would I be able to access the App Store and run current programs and codecs or would I still be limited? Since Mac apps are all .dmg files, it hard to know what works.

i was in the same boat, in 2011 and all my programs (CS$4) worked except a scanning and photo app i got from another source.
IF you have a external HD, plug that into a apple store book and see what is visible, most of the app are.
good luck!

yes you can access the app store no it won't do you much of any good unless your running mavericks or yosemite apple likes to update there app store to the latest o.s and if you are out of date lets say on snow leopard or lion you can't download the latest apps sorry

Does the apps in the App Store only work with Mavericks and Yosemite? Surely, Apple doesn't change all there apps or do they?

Changing the minimum OS that an app needs is up to the developer not Apple (except apps such as Pages made by Apple).

You can still find apps that run under 10.6. If you upgrade beyond 10.6.8 you won't be able to run your Power PC apps though you should be able to access the data from those programs.